Exo-endo cellulase fusion protein

ABSTRACT

The present invention relates to a heterologous exo-endo cellulase fusion construct, which encodes a fusion protein having cellulolytic activity comprising a catalytic domain derived from a fungal exo-cellobiohydrolase and a catalytic domain derived from an endoglucanase. The invention also relates to vectors and fungal host cells comprising the heterologous exo-endo cellulase fusion construct as well as methods for producing a cellulase fusion protein and enzymatic cellulase compositions.

RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 60/556,598, entitled “Exo-Endo Cellulase FusionProtein” and filed on Mar. 25, 2004.

SPONSORED RESEARCH AND DEVELOPMENT

Portions of this work were funded by Subcontract No. ZC0-0-30017-01 withthe National Renewable Energy Laboratory under Prime Contract No.DE-AC36-99G010337 with the United States Department of Energy.Accordingly, the United States Government may have certain rights in theinvention.

FIELD OF THE INVENTION

The present invention relates to a heterologous exo-endo cellulasefusion construct, which encodes a fusion protein having cellulolyticactivity comprising a catalytic domain derived from a fungalexo-cellobiohydrolase and a catalytic domain derived from anendoglucanase. The invention also relates to vectors and fungal hostcells comprising the heterologous exo-endo cellulase fusion construct aswell as methods for producing a cellulase fusion protein and enzymaticcellulase compositions.

BACKGROUND OF THE INVENTION

Cellulose and hemicellulose are the most abundant plant materialsproduced by photosynthesis. They can be degraded and used as an energysource by numerous microorganisms, including bacteria, yeast and fungi,which produce extracellular enzymes capable of hydrolysis of thepolymeric substrates to monomeric sugars (Aro et al., 2001). As thelimits of non-renewable resources approach, the potential of celluloseto become a major renewable energy resource is enormous (Krishna at al.,2001). The effective utilization of cellulose through biologicalprocesses is one approach to overcoming the shortage of foods, feeds,and fuels (Ohmiya et al., 1997).

Cellulases are enzymes that hydrolyze cellulose (beta-1,4-glucan or betaD-glucosidic linkages) resulting in the formation of glucose,cellobiose, cellooligosaccharides, and the like. Cellulases have beentraditionally divided into three major classes: endoglucanases (EC3.2.1.4) (“EG”), exoglucanases or cellobiohydrolases (EC 3.2.1.91)(“CBH”) and beta-glucosidases ((beta)-D-glucoside glucohydrolase; EC3.2.1.21) (“BG”) (Knowles et al., 1987 and Schulein, 1988).Endoglucanases act mainly on the amorphous parts of the cellulose fiber,whereas cellobiohydrolases are also able to degrade crystallinecellulose.

Cellulases are known to be produced by a large number of bacteria, yeastand fungi. Certain fungi produce a complete cellulase system capable ofdegrading crystalline forms of cellulose, such that the cellulases arereadily produced in large quantities via fermentation.

In order to efficiently convert crystalline cellulose to glucose thecomplete cellulase system comprising components from each of the CBH, EGand BG classifications is required, with isolated components lesseffective in hydrolyzing crystalline cellulose (Filho et al., 1996). Inparticular, the combination of EG-type cellulases and CBH-typecellulases interact to more efficiently degrade cellulose than eitherenzyme used alone (Wood, 1985; Baker et al., 1994; and Nieves et al.,1995).

Additionally, cellulases are known in the art to be useful in thetreatment of textiles for the purposes of enhancing the cleaning abilityof detergent compositions, for use as a softening agent, for improvingthe feel and appearance of cotton fabrics, and the like (Kumar et al.,1997). Cellulase-containing detergent compositions with improvedcleaning performance (U.S. Pat. No. 4,435,307; GB App. Nos. 2,095,275and 2,094,826) and for use in the treatment of fabric to improve thefeel and appearance of the textile (U.S. Pat. Nos. 5,648,263, 5,691,178,and 5,776,757, and GB App. No. 1,358,599), have been described in theliterature.

Hence, cellulases produced in fungi and bacteria have receivedsignificant attention. In particular, fermentation of Trichoderma spp.(e.g., Trichoderma longibrachiatum or Trichoderma reesei) has been shownto produce a complete cellulase system capable of degrading crystallineforms of cellulose. Over the years, Trichoderma cellulase production hasbeen improved by classical mutagenesis; screening, selection anddevelopment of highly refined, large scale inexpensive fermentationconditions. While the multi-component cellulase system of Trichodermaspp. is able to hydrolyze cellulose to glucose, there are cellulasesfrom other microorganisms, particularly bacterial strains, withdifferent properties for efficient cellulose hydrolysis, and it would beadvantageous to express these proteins in a filamentous fungus forindustrial scale cellulase production. However, the results of manystudies demonstrate that the yield of bacterial enzymes from filamentousfungi is low (Jeeves et al., 1991).

In this invention, a heterologous exo-endo cellulase fusion construct,which includes the coding region of a fungal exo-cellobiohydrolase (CBH)catalytic domain and a coding region of an endoglucanase (EG) catalyticdomain, has been introduced and expressed in a filamentous fungi hostcell to increase the yield and effectiveness of cellulase enzymes.

SUMMARY OF THE INVENTION

In a first aspect, the invention includes a heterologous exo-endocellulase fusion construct comprising in operable linkage from the 5′end of said construct, (a) a DNA molecule encoding a signal sequence,(b) a DNA molecule encoding a catalytic domain of anexo-cellobiohydrolase, and (c) a DNA molecule encoding an endoglucanasecatalytic domain.

In a first embodiment of this aspect, the heterologous exo-endocellulase fusion construct further comprises a linker sequence located3′ of the catalytic domain of the exo-cellobiohydrolase and 5′ of thecatalytic domain of the endoglucanase. In a second embodiment, theheterologous exo-endo cellulase fusion construct lacks the cellulosebinding domain (CBD) of the exo-cellobiohydrolase. In a thirdembodiment, the heterologous exo-endo cellulase fusion construct furthercomprises a kexin site located after the linker sequence and before thecoding region of the endoglucanase catalytic domain. In a fourthembodiment, the heterologous exo-endo fusion construct will comprise apromoter of a filamentous fungus secretable protein, said promoterlocated in operable linkage 5′ of the coding region of theexo-cellobiohydrolase catalytic domain. In a fifth embodiment, thepromoter is a cbh promoter and preferably a cbh1 promoter derived fromT. reesei. In a sixth embodiment, the exo-cellobiohydrolase is a CBH1and particularly a CBH1 having an amino acid sequence of at least 90%sequence identity with the sequence set forth in SEQ ID NO.: 6. In aseventh embodiment, the endoglucanase catalytic domain is derived from abacterial endoglucanase. In an eighth embodiment, the bacterialendoglucanase catalytic domain is selected from the group consisting ofan Acidothermus cellulolyticus GH5A endoglucanase I (E1) catalyticdomain; an Acidothermus cellulolyticus GH74 endoglucanase (GH74-EG)catalytic domain: and a Thermobifida fusca E5 endoglucanase (Tf-E5)catalytic domain. In a ninth embodiment, the heterologous exo-endocellulase fusion construct lacks the cellulose binding domain of theendoglucanase. In a tenth embodiment, the endoglucanase is anAcidothermus cellulolyticus GH5A E1 and particularly the Acidothermuscellulolyticus GH5A E1 having an amino acid sequence of at least 90%sequence identity with the sequence set forth in SEQ ID NO. 8. In aneleventh embodiment, the heterologous exo-endo cellulase fusionconstruct comprises a terminator sequence located 3′ to theendoglucanase catalytic domain. In a twelfth embodiment, theheterologous fusion construct comprises a selectable marker.

In a second aspect, the invention includes a vector comprising inoperable linkage a promoter of a filamentous fungus secretable protein,a DNA molecule encoding a signal sequence, a DNA molecule encoding acatalytic domain of a fungal exo-cellobiohydrolase, a DNA moleculeencoding a catalytic domain of an endoglucanase, and a terminator. Inone embodiment, the vector will further include a selectable marker.

In a second embodiment, the vector will comprise a linker located 3′ ofthe exo-cellobiohydrolase (CBH) catalytic domain and 5′ of the EGcatalytic domain. In a third embodiment, the vector will lack the CBHcellulose binding domain. In a fourth embodiment, the vector willcomprise a kexin site. In a fifth embodiment, the catalytic domain ofthe endoglucanase is derived from a bacterial endoglucanase. In a sixthembodiment, the vector lacks the cellulose binding domain of theendoglucanase.

In a third aspect, the invention includes a fungal host cell transformedwith a heterologous exo-endo cellulase fusion construct or a fungal hostcell transformed with a vector comprising a heterologous exo-endocellulase fusion construct.

In a fourth aspect, the invention includes a recombinant fungal cellcomprising the heterologous exo-end cellulase fusion construct or avector comprising the same.

In a particularly preferred embodiment of the third and fourth aspects,the fungal host cell is a Trichoderma host cell and more particularly astrain of T. reesei. In another embodiment of these aspects, nativecellulase genes, such as cbh1, cbh2, egl1 and egl2 have been deletedfrom the fungal cells. In a third embodiment, the native cellulosebinding domain has been deleted from the fungal cells.

In a fifth aspect, the invention includes an isolated cellulase fusionprotein having cellulolytic activity which comprises anexo-cellobiohydrolase catalytic domain and an endoglucanase catalyticdomain, wherein the exo-cellobiohydrolase lacks a cellulose bindingdomain. In one embodiment of this aspect, the exo-cellobiohydrolase is aCBH1. In a second embodiment, the catalytic domain of the endoglucanaseis derived from a bacterial cell. In a third embodiment, the bacterialcell is a strain of Acidothermus cellulolyticus. In a fourth embodiment,the invention concerns a cellulolytic composition comprising theisolated cellulase fusion protein.

In a sixth aspect, the invention includes a method of producing anenzyme having cellulolytic activity comprising, a) stably transforming afilamentous fungal host cell with a heterologous exo-endo cellulasefusion construct or vector as defined above in the first aspect andsecond aspect; b) cultivating the transformed fungal host cell underconditions suitable for said fungal host cell to produce an enzymehaving cellulolytic activity; and c) recovering said enzyme.

In one embodiment of this aspect, the filamentous fungal host cell is aTrichoderma cell, and particularly a T. reesei host cell. In a secondembodiment, the exo-cellobiohydrolase is a CBH1 and the endoglucanase isan Acidothermus cellulolyticus endoglucanase or a Thermobifida fuscaendoglucanase. In a third embodiment, the recovered enzyme is acellulase fusion protein, components of the cellulase fusion protein, ora combination of the cellulase fusion protein and the componentsthereof. In a fourth embodiment, the recovered enzyme(s) is purified.

In an seventh aspect, the invention includes a Trichoderma host cellwhich expresses a cellulase fusion protein, wherein said fusion proteincomprises a catalytic domain of an exo-cellobiohydrolase and a catalyticdomain of an endoglucanase, wherein the exo-cellobiohydrolase lacks acellulose binding domain. In one embodiment, the Trichoderma host cellis a T. reesei cell. In a second embodiment, the exo-cellobiohydrolaseis a CBH1 and the endoglucanase is an Acidothermus cellulolyticusendoglucanase and particularly an Acidothermus cellulolyticus E1 or GH74endoglucanase. In a third embodiment, the endoglucanase lacks acellulose binding domain. In a fourth embodiment, the T. reesei hostcell includes deleted native cellulase genes.

In an eighth aspect, the invention includes a fungal cellulasecomposition comprising a cellulase fusion protein or components thereof,wherein the fusion protein or components thereof is the product of arecombinant Trichoderma spp. In one embodiment, the cellulase fusionprotein is a CBH1-Acidothermus cellulolyticus E1 fusion protein and thecomponents are the cleaved products, CBH1 and Acidothermuscellulolyticus E1, wherein each component has cellulolytic activity.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a representation of a heterologous exo-endo cellulase fusionconstruct encompassed by the invention, which includes a Trichodermareesei cbh1 promoter, a cbh1 core (cbh1 signal sequence and cbh1catalytic domain), a cbh1 linker sequence, a kexin site, an E1 core (anAcidothermus cellulolyticus E1 endoglucanase catalytic domain), a cbh1terminator and an A. nidulans amdS selectable marker.

FIG. 2 is a DNA sequence (SEQ ID NO: 1) of the T. reesei cbh1 signalsequence (SEQ ID NO: 2); the T. reesei cbh1 catalytic domain (SEQ ID NO:3), and the T. reesei cbh1 linker (SEQ ID NO: 4). The signal sequence isunderlined, the catalytic domain is in bold, and the linker sequence isin italics.

FIG. 3 shows the predicted amino acid sequence (SEQ ID NO: 5) based onthe nucleotide sequence provided in FIG. 2, wherein the signal peptideis underlined, the catalytic domain, represented by (SEQ ID NO: 6), isin bold, and the linker is in italics.

FIG. 4 is an illustration of a nucleotide sequence (SEQ ID NO: 7)encoding an Acidothermus cellulolyticus GH5A endoglucanase I (E1))catalytic domain.

FIG. 5 is the predicted amino acid sequence (SEQ ID NO: 8) of theAcidothermus cellulolyticus GH5A E1 catalytic domain based on thenucleotide sequence provided in FIG. 4.

FIGS. 6A and 6B are an illustration of a nucleotide sequence (SEQ ID NO:9) encoding an Acidothermus cellulolyticus GH74-EG catalytic domain.

FIG. 7 is the predicted amino acid sequence (SEQ ID NO: 10) of theAcidothermus cellulolyticus GH74-EG based on the nucleotide sequenceprovided in FIGS. 6A and 6B.

FIG. 8 is an illustration of a nucleotide sequence (SEQ ID NO: 11)encoding the CBD, linker and catalytic domain of endoglucanase 5 (E5) ofThermobifida fusca.

FIG. 9 is the predicted amino acid sequence (SEQ ID NO: 12) of the CBD,linker and E5 based on the nucleotide sequence provided in FIG. 8.

FIG. 10 is the nucleotide sequence (2656 bases) (SEQ ID NO: 13) of aheterologous cellulase fusion construct described in example 1comprising, the T. reesei CBH1 signal sequence; the catalytic domain ofthe T. reesei CBH1; the T. reesei CBH1 linker sequence; a kexin cleavagesite which includes codons for the amino acids SKR and the sequencecoding for the Acidothermus cellulolyticus GH5A-E1 catalytic domain.

FIG. 11 is the predicted amino acid sequence (SEQ ID NO: 14) of thecellulase fusion protein based on the nucleic acid sequence in FIG. 10.

FIG. 12 provides a schematic diagram of the pTrex4 plasmid, which wasused for expression of a heterologous exo-endo cellulase fusionconstruct (CBH1-endoglucanase) as described in the examples and includesthe Trichoderma reesei cbh1 promoter, the T. reesei CBH1 signalsequence, catalytic domain, and linker sequences, a kexin cleavage siteand an endoglucanase gene of interest inserted between a SpeI and AscIsite, a CBH1 Trichoderma reesei terminator and the amdS Aspergillusnidulans acetamidase marker gene.

FIGS. 13A-E provide the nucleotide sequence (SEQ ID NO:15) (10239 bp) ofthe pTrex4 plasmid of FIG. 12 without the catalytic domain of the EGgene of interest.

FIG. 14 illustrates a SDS-PAGE gel of supernate samples of shake flaskgrowth of clones of a T. reesei strain deleted for the cellulases, cbh1,cbh2, egl1 and egl2 and transformed with the CBH1-E1 fusion construct.Lanes 1 and 10 represent MARK 12 Protein Standard (Invitrogen, Carlsbad,Calif.). Lanes 2-8 represent various transformants and lane 9 representsthe untransformed T. reesei strain. The upper arrow indicates thecellulase fusion protein and the lower arrow indicates the cleaved E1catalytic domain.

FIG. 15 illustrates a SDS-PAGE gel of supernate samples of shake flaskgrowth of clones of a T. reesei strain deleted for the cellulases, cbh1,cbh2, egl1 and egl2 and transformed with the CBH1-GH74 fusion construct.Lane 1 represents the untransformed control. Lane 3 represents MARK 12Protein Standard (Invitrogen, Carlsbad, Calif.). Lanes 2 and 4-12represent various transformants. The upper arrow indicates the CBH1-GH74fusion protein and the lower arrow indicates the cleaved GH74 catalyticdomain.

FIG. 16 illustrates a SDS-PAGE gel of supernate samples of shake flaskgrowth of clones of a T. reesei strain deleted for the cellulases, cbh1,cbh2, egl1 and egl2 and transformed with the CBH1-TfE5 fusion construct.Lane1 represents MARK 12 Protein Standard (Invitrogen, Carlsbad,Calif.). Lane 2 represents the untransformed strain and lanes 3-12represent various transformants. Arrows indicate new bands observed inthe CBH1-TfE5 expressing transformants.

FIG. 17 illustrates the % cellulose conversion to soluble sugars overtime for a T. reesei parent strain comprising native cellulase geneswith a corresponding T. reesei strain which expresses the CBH1-E1 fusionprotein and reference is made to example 3.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described in detail by way of reference onlyusing the following definitions and examples. All patents andpublications, including all sequences disclosed within such patents andpublications, referred to herein are expressly incorporated byreference.

Unless defined otherwise herein, all technical and scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which this invention belongs. Singleton, et al.,DICTIONARY OF MICROBIOLOGY AND MOLECULAR BIOLOGY, 2D ED., John Wiley andSons, New York (1994), and Hale & Marham, THE HARPER COLLINS DICTIONARYOF BIOLOGY, Harper Perennial, NY (1991) provide one of skill with ageneral dictionary of many of the terms used in this invention.Practitioners are particularly directed to Sambrook et al., MOLECULARCLONING: A LABORATORY MANUAL (Second and Third Editions (1989 and 2001),Cold Spring Harbor Press, Plainview, N.Y., and Ausubel F M et al.,Current Protocols in Molecular Biology, John Wiley & Sons, New York,N.Y., 1993, for definitions and terms of the art.

It is to be understood that this invention is not limited to theparticular methodology, protocols, and reagents described, as these mayvary. Although any methods and materials similar or equivalent to thosedescribed herein can be used in the practice or testing of the presentinvention, the preferred methods and materials are described.

Numeric ranges are inclusive of the numbers defining the range. Unlessotherwise indicated, nucleic acids are written left to right in 5′ to 3′orientation; amino acid sequences are written left to right in amino tocarboxy orientation, respectively.

Other objects, features and advantages of the present invention willbecome apparent from the following detailed description. It should beunderstood, however, that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the scope and spirit of the invention will becomeapparent to one skilled in the art from this detailed description.

1. DEFINITIONS

The term “heterologous exo-endo cellulase fusion construct” refers to anucleic acid construct that is composed of parts of different genes inoperable linkage. The components include, from the 5′ end, a DNAmolecule encoding an exo-cellobiohydrolase catalytic domain and a DNAmolecule encoding an endoglucanase catalytic domain.

The term “cellulase fusion protein” or “fusion protein havingcellulolytic activity” refers to an enzyme, which has anexo-cellobiohydrolase catalytic domain and an endoglucanase catalyticdomain and exhibits cellulolytic activity. The term “components of acellulase fusion protein” refers to individual (cleaved) fragments ofthe cellulase fusion protein, wherein each fragment has cellulolyticactivity and includes one of the catalytic domains of the fusionprotein.

The term “cellulase” refers to a category of enzymes capable ofhydrolyzing cellulose (beta-1,4-glucan or beta D-glucosidic linkages)polymers to shorter cello-oligosaccharide oligomers, cellobiose and/orglucose.

The term “exo-cellobiohydrolase” (CBH) refers to a group of cellulaseenzymes classified as EC 3.2.1.91. These enzymes are also known asexoglucanases or cellobiohydrolases. CBH enzymes hydrolyze cellobiosefrom the reducing or non-reducing end of cellulose. In general, a CBH1type enzyme preferentially hydrolyzes cellobiose from the reducing endof cellulose and a CBH2 type enzyme preferentially hydrolyzes thenon-reducing end of cellulose.

The term “endoglucanase” (EG) refers to a group of cellulase enzymesclassified as EC 3.2.1.4. An EG enzyme hydrolyzes internal beta-1,4glucosidic bonds of the cellulose.

The term “beta-glucosidases” refers to a group of cellulase enzymesclassified as EC 3.2.1.21.

“Cellulolytic activity” encompasses exoglucanase activity, endoglucanaseactivity or both types of enzymatic activity.

The term “catalytic domain” refers to a structural portion or region ofthe amino acid sequence of a cellulase which possess the catalyticactivity of the cellulase. The catalytic domain is a structural elementof the cellulase tertiary structure that is distinct from the cellulosebinding domain or site, which is a structural element which binds thecellulase to a substrate, such as cellulose.

The term “cellulose binding domain (CBD)” as used herein refers to aportion of the amino acid sequence of a cellulase or a region of theenzyme that is involved in the cellulose binding activity of acellulase. Cellulose binding domains generally function bynon-covalently binding the cellulase to cellulose, a cellulosederivative or other polysaccharide equivalent thereof. CBDs typicallyfunction independent of the catalytic domain.

A nucleic acid is “operably linked” when it is placed into a functionalrelationship with another nucleic acid sequence. For example, DNAencoding a signal peptide is operably linked to DNA encoding apolypeptide if it is expressed as a preprotein that participates in thesecretion of the polypeptide; a promoter is operably linked to a codingsequence if it affects the transcription of the sequence. Generally,“operably linked” means that the DNA sequences being linked arecontiguous, and, in the case of the heterologous exo-endo cellulasefusion construct contiguous and in reading frame.

As used herein, the term “gene” means the segment of DNA involved inproducing a polypeptide chain, that may or may not include regionspreceding and following the coding region, e.g. 5′ untranslated (5′ UTR)or “leader” sequences and 3′ UTR or “trailer” sequences, as well asintervening sequences (introns) between individual coding segments(exons).

The term “polypeptide” as used herein refers to a compound made up of asingle chain of amino acid residues linked by peptide bonds. The term“protein” as used herein may be synonymous with the term “polypeptide”or may refer, in addition, to a complex of two or more polypeptides.

The term “nucleic acid molecule”, “nucleic acid” or “polynucleotide”includes RNA, DNA and cDNA molecules. It will be understood that, as aresult of the degeneracy of the genetic code, a multitude of nucleotidesequences encoding a given protein such as a cellulase fusion protein ofthe invention may be produced.

A “heterologous” nucleic acid sequence has a portion of the sequence,which is not native to the cell in which it is expressed. For example,heterologous, with respect to a control sequence refers to a controlsequence (i.e. promoter or enhancer) that does not function in nature toregulate the same gene the expression of which it is currentlyregulating. Generally, heterologous nucleic acid sequences are notendogenous to the cell or part of the genome in which they are present,and have been added to the cell, by infection, transfection,transformation, microinjection, electroporation, or the like. A“heterologous” nucleic acid sequence may contain a control sequence/DNAcoding sequence combination that is the same as, or different from acontrol sequence/DNA coding sequence combination found in the nativecell. The term heterologous nucleic acid sequence encompasses aheterologous exo-endo cellulase fusion construct according to theinvention.

As used herein, the term “vector” refers to a nucleic acid sequence orconstruct designed for transfer between different host cells. An“expression vector” refers to a vector that has the ability toincorporate and express heterologous DNA sequences in a foreign cell. Anexpression vector may be generated recombinantly or synthetically, witha series of specified nucleic acid elements that permit transcription ofa particular nucleic acid in a target cell. The recombinant expressioncassette can be incorporated into a plasmid, chromosome, mitochondrialDNA, virus, or nucleic acid fragment.

As used herein, the term “plasmid” refers to a circular double-stranded(ds) DNA construct used as a cloning vector, and which forms anextrachromosomal self-replicating genetic element in many bacteria andsome eukaryotes.

As used herein, the term “selectable marker” refers to a nucleotidesequence which is capable of expression in cells and where expression ofthe selectable marker confers to cells containing the expressed gene theability to grow in the presence of a corresponding selective agent, orunder corresponding selective growth conditions.

As used herein, the term “promoter” refers to a nucleic acid sequencethat functions to direct transcription of a downstream gene. Thepromoter will generally be appropriate to the host cell in which thetarget gene is being expressed. The promoter together with othertranscriptional and translational regulatory nucleic acid sequences(also termed “control sequences”) are necessary to express a given gene.In general, the transcriptional and translational regulatory sequencesinclude, but are not limited to, promoter sequences, ribosomal bindingsites, transcriptional start and stop sequences, translational start andstop sequences, and enhancer or activator sequences.

The term “signal sequence” or “signal peptide” refers to a sequence ofamino acids at the N-terminal portion of a protein, which facilitatesthe secretion of the mature form of the protein outside the cell. Themature form of the extracellular protein lacks the signal sequence whichis cleaved off during the secretion process.

By the term “host cell” is meant a cell that contains a heterologousexo-endo cellulase fusion construct encompassed by the invention or avector including the same and supports the replication, and/ortranscription or transcription and translation (expression) of theheterologous exo-endo cellulase construct. Host cells for use in thepresent invention can be prokaryotic cells, such as E. coli, oreukaryotic cells such as yeast, plant, insect, amphibian, or mammaliancells. In general, host cells are filamentous fungi.

The term “filamentous fungi” includes all filamentous fungi recognizedby those of skill in the art. A preferred fungus is selected from thesubdivision Eumycota and Oomycota and particularly from the groupconsisting of Aspergillus, Trichoderma, Fusarium, Chrysosporium,Penicillium, Humicola, Neurospora, or alternative sexual forms thereofsuch as Emericella and Hypocrea (See, Kuhls et al., 1996).

The filamentous fungi are characterized by vegetative mycelium having acell wall composed of chitin, glucan, chitosan, mannan, and othercomplex polysaccharides, with vegetative growth by hyphal elongation andcarbon catabolism that is obligately aerobic.

The term “derived” encompasses the terms originated from, obtained orobtainable from and isolated from.

An “equivalent” amino acid sequence is an amino acid sequence that isnot identical to an original reference amino acid sequence but includessome amino acid changes, which may be substitutions, deletions,additions or the like, wherein the protein exhibits essentially the samequalitative biological activity of the reference protein. An equivalentamino acid sequence will have between 80%-99% amino acid identity to theoriginal reference sequence. Preferably the equivalent amino acidsequence will have at least 85%, 90%, 93%, 95%, 96%, 98% and 99%identity to the reference sequence.

A “substitution” results from the replacement of one or more nucleotidesor amino acid by different nucleotides or amino acids, respectively.Substitutions are usually made in accordance with known conservativesubstitutions, wherein one class of amino acid is substituted with anamino acid in the same class. A “non-conservative substitution” refersto the substitution of an amino acid in one class with an amino acidfrom another class.

A “deletion” is a change in a nucleotide or amino acid sequence in whichone or more nucleotides or amino acids are absent.

An “addition” is a change in a nucleotide or amino acid sequence thathas resulted from the insertion of one or more nucleotides or amino acidas compared to an original reference sequence.

As used herein, “recombinant” includes reference to a cell or vector,that has been modified by the introduction of heterologous nucleic acidsequences or that the cell is derived from a cell so modified. Thus, forexample, recombinant cells express genes that are not found in identicalform within the native (non-recombinant) form of the cell or expressnative genes that are otherwise abnormally expressed, under expressed ornot expressed at all as a result of deliberate human intervention.

As used herein, the terms “transformed”, “stably transformed” or“transgenic” with reference to a cell means the cell has a heterologousnucleic acid sequence according to the invention integrated into itsgenome or as an episomal plasmid that is maintained through multiplegenerations.

The term “introduced” in the context of inserting a heterologousexo-endo cellulase fusion construct or heterologous nucleic acidsequence into a cell, means “transfection”, “transformation” or“transduction” and includes reference to the incorporation of aheterologous nucleic acid sequence or heterologous exo-endo cellulasefusion construct into a eukaryotic or prokaryotic cell where theheterologous nucleic acid sequence or heterologous exo-endo cellulasenucleic acid construct may be incorporated into the genome of the cell(for example, chromosome, plasmid, plastid, or mitochondrial DNA),converted into an autonomous replicon, or transiently expressed (forexample, transfected mRNA).

As used herein, the term “expression” refers to the process by which apolypeptide is produced based on the nucleic acid sequence of a gene.The process includes both transcription and translation.

It follows that the term “cellulase fusion protein expression” or“fusion expression” refers to transcription and translation of a“heterologous exo-endo cellulase fusion construct” comprising thecatalytic domain of an exo-cellobiohydrolase and the catalytic domain ofan endoglucanase, the products of which include precursor RNA, mRNA,polypeptide, post-translationally processed polypeptides, andderivatives thereof.

As used herein, the term “purifying” generally refers to subjectingrecombinant nucleic acid or protein containing cells to biochemicalpurification and/or column chromatography.

As used herein, the terms “active” and “biologically active” refer to abiological activity associated with a particular protein, such as theenzymatic activity associated with a cellulase. It follows that thebiological activity of a given protein refers to any biological activitytypically attributed to that protein by those of skill in the art.

As used herein, the term “enriched” means that the concentration of acellulase enzyme found in a fungal cellulase composition is greaterrelative to the concentration found in a wild type or naturallyoccurring fungal cellulase composition. The terms enriched, elevated andenhanced may be used interchangeably herein.

A “wild type fungal cellulase composition” is one produced by anaturally occurring fungal source and which comprises one or more BG,CBH and EG components wherein each of these components is found at theratio produced by the fungal source.

Thus, to illustrate, a naturally occurring cellulase system may bepurified into substantially pure components by recognized separationtechniques well published in the literature, including ion exchangechromatography at a suitable pH, affinity chromatography, size exclusionand the like. A purified cellulase fusion protein or components thereofmay then be added to the enzymatic solution resulting in an enrichedcellulase solution. It is also possible to elevate the amount of EG orCBH produced by a microbe by expressing a cellulase fusion proteinencompassed by the invention.

“A”, “an” and “the” include plural references unless the context clearlydictates otherwise.

As used herein the term “comprising” and its cognates are used in theirinclusive sense: that is equivalent to the term “including” and itscorresponding cognates.

“ATCC” refers to American Type Culture Collection located in ManassasVa. 20108 (ATCC www/atcc.org).

“NRRL” refers to the Agricultural Research Service Culture Collection,National Center for Agricultural utilization Research (and previouslyknown as USDA Northern Regional Research Laboratory), Peoria, Ill.

2. PREFERRED EMBODIMENTS A. Components and Construction of HeterologousExo-Endo Cellulase Fusion Constructs and Expression Vectors.

A heterologous exo-endo cellulase fusion construct or a vectorcomprising a heterologous exo-endo cellulase fusion construct may beintroduced into and replicated in a filamentous fungal host cell forprotein expression and secretion.

In some embodiments, the heterologous exo-endo cellulase fusionconstruct comprises in operable linkage from the 5′ end of saidconstruct, optionally a signal peptide, a DNA molecule encoding acatalytic domain of an exo-cellobiohydrolase, and a DNA moleculeencoding a catalytic domain of an endoglucanase. In other embodiments,the components of the heterologous exo-endo cellulase fusion constructcomprise in operable linkage from the 5′ end of said construct,optionally a signal peptide, a DNA molecule encoding a catalytic domainof an exo-cellobiohydrolase, optionally a DNA molecule encoding the CBDof an endoglucanase, and a DNA molecule encoding a catalytic domain ofthe endoglucanase.

In other embodiments the construct will comprise in operable linkagefrom the 5′ end of said construct optionally a signal peptide, a DNAmolecule encoding a catalytic domain of an exo-cellobiohydrolase,optionally a DNA molecule encoding the CBD of the exo-cellobiohydrolase,a linker, optionally a DNA molecule encoding the CBD of anendoglucanase, and a DNA molecule encoding a catalytic domain of theendoglucanase.

In a further embodiment the heterologous exo-endo cellulase fusionconstruct or vector comprising a heterologous exo-endo cellulase fusionconstruct includes in operable linkage from the 5′ end, a promoter of afilamentous fungus secretable protein; a DNA molecule encoding a signalsequence; a DNA molecule encoding a catalytic domain of anexo-cellobiohydrolase, optionally a DNA molecule encoding theexo-cellobiohydrolase CBD; a DNA molecule encoding a catalytic domain ofan endoglucanase; and a terminator. Further the vector may include a DNAmolecule encoding the CBD of the endoglucanase said CBD located 5′ tothe DNA molecule encoding the endoglucanase catalytic domain.

In one embodiment a preferred heterologous exo-endo cellulase fusionconstruct or expression vector will not include theexo-cellobiohydrolase CBD. In another embodiment, a preferred expressionvector will include a promoter of a filamentous fungus secretableprotein, a DNA molecule encoding an exo-cellobiohydrolase signalsequence, a DNA molecule encoding a catalytic domain of anexo-cellobiohydrolase, a linker, a DNA molecule encoding a catalyticdomain of an endoglucanase, and a terminator, wherein the vector lacksthe CBD of the exo-cellobiohydrolase and optionally lacks the CBD of theendoglucanase. In a preferred embodiment, the coding sequence for theendoglucanase catalytic domain (either including the endoglucanase CBDor lacking the endoglucanase CBD) will not include an endoglucanasesignal sequence. Reference is made to FIGS. 1, 10 and 12 as examples ofembodiments including an expression vector and heterologous exo-endocellulase fusion construct of the invention.

Exemplary promoters include both constitutive promoters and induciblepromoters. Examples include the promoters from the Aspergillus niger, A.awamori or A. oryzae glucoamylase, alpha-amylase, or alpha-glucosidaseencoding genes; the A. nidulans gpdA or trpC genes; the Neurosporacrassa cbh1 or trp1 genes; the A. niger or Rhizomucor miehei asparticproteinase encoding genes; the T. reesei cbh1, cbh2, egl1, egl2, orother cellulase encoding genes; a CMV promoter, an SV40 early promoter,an RSV promoter, an EF-1α promoter, a promoter containing the tetresponsive element (TRE) in the tet-on or tet-off system as described(ClonTech and BASF), the beta actin promoter. In some embodiments thepromoter is one that is native to the fungal host cell to betransformed.

In one preferred embodiment, the promoter is an exo-cellobiohydrolasecbh1 or cbh2 promoter and particularly a cbh1 promoter, such as a T.reesei cbh1 promoter. The T. reesei cbh1 promoter is an induciblepromoter, and reference is made to GenBank Accession No. D86235.

The DNA sequence encoding an exo-cellobiohydrolase catalytic domain isoperably linked to a DNA sequence encoding a signal sequence. The signalsequence is preferably that which is naturally associated with theexo-cellobiohydrolase to be expressed. Preferably the signal sequence isencoded by a Trichoderma or Aspergillus gene which encodes a CBH. Morepreferably the signal sequence is encoded by a Trichoderma gene whichencodes a CBH1. In further embodiments, the promoter and signal sequenceof the heterologous exo-endo cellulase fusion construct are derived fromthe same source. In some embodiments, the signal sequence is aTrichoderma cbh1 signal sequence that is operably linked to aTrichoderma cbh1 promoter. In further embodiments the signal sequencehas the amino acid sequence of SEQ ID NO: 2 or an equivalent sequence ora sequence having at least 95% identity thereto.

Most exo-cellobiohydrolases (CBHs) and endoglucanases (EGs) have amultidomain structure consisting of a catalytic domain separated from acellulose binding domain (CBD) by a linker peptide (Suurnakki et al.,2000). The catalytic domain contains the active site whereas the CBDinteracts with cellulose by binding the enzyme to it (van Tilbeurgh etal., 1986 and Tomme et al., 1988).

Numerous cellulases have been described in the scientific literature,examples of which include: from Trichoderma reesei: Shoemaker, S. etal., Bio/Technology, 1:691-696, 1983, which discloses CBH1; Teeri, T. etal., Gene, 51:43-52, 1987, which discloses CBH2; Penttila, M. et al.,Gene, 45:253-263, 1986, which discloses EG1; Saloheimo, M. et al., Gene,63:11-22, 1988, which discloses EG2; Okada, M. et al., Appl. Environ.Microbiol., 64:555-563, 1988, which discloses EG3; Saloheimo, M. et al.,Eur. J. Biochem., 249:584-591, 1997, which discloses EG4; and Saloheimo,A. et al., Molecular Microbiology, 13:219-228, 1994, which disclosesEG5. Exo-cellobiohydrolases and endoglucanases from species other thanTrichoderma have also been described e.g., Ooi et al., 1990, whichdiscloses the cDNA sequence coding for endoglucanase F1-CMC produced byAspergillus aculeatus; Kawaguchi T et al., 1996, which discloses thecloning and sequencing of the cDNA encoding beta-glucosidase 1 fromAspergillus aculeatus; Sakamoto et al., 1995, which discloses the cDNAsequence encoding the endoglucanase CMCase-1 from Aspergillus kawachiiIFO 4308; and Saarilahti et al., 1990 which discloses an endoglucanasefrom Erwinia carotovara. The sequences encoding these enzymes may beused in the heterologous exo-endo cellulase fusion construct or vectorof the invention.

In some embodiments, the catalytic domain is derived from a CBH1 typeexo-cellobiohydrolase and in other embodiments the catalytic domain isderived from a CBH2 type exo-cellobiohydrolase. In some embodiments, theCBH1 or CBH2 catalytic domain is derived from a Trichoderma spp.

In one embodiment, the catalytic domain of an exo-cellobiohydrolase isencoded by a nucleic acid sequence of a Trichoderma reesei cbh1. In someembodiments the nucleic acid is the sequence of SEQ ID NO:3 andnucleotide sequences homologous thereto.

In other embodiments, the catalytic domain will have the amino acidsequence of SEQ ID NO: 6 and equivalent amino acid sequences thereto.Further DNA sequences encoding any equivalents of said amino acidsequences of SEQ ID NO: 6, wherein said equivalents have a similarqualitative biological activity to SEQ ID NO: 6 may be incorporated intothe heterologous exo-endo cellulase fusion construct.

In some embodiments, heterologous exo-endo cellulase fusion constructsencompassed by the invention will include a linker located 3′ to thesequence encoding the exo-cellobiohydrolase catalytic domain and 5′ tothe sequence encoding the endoglucanase catalytic domain. In somepreferred embodiments, the linker is derived from the same source as thecatalytic domain of the exo-cellobiohydrolase. Preferably the linkerwill be derived from a Trichoderma cbh1 gene. One preferred linkersequence is illustrated in FIG. 3. In other embodiments, theheterologous exo-endo cellulase fusion construct will include two ormore linkers. For example a linker may be located not only between thecoding sequence of the CBH catalytic domain and the coding sequence ofthe EG catalytic domain but also between the coding region of the CBHCBD and the coding region of the EG CBD. Further linkers may be locatedbetween the CBD of the endoglucanase and the catalytic domain of theendoglucanase. In general, a linker may be between about 5 to 60 aminoacid residues, between about 15 to 50 amino acid residues, and betweenabout 25 to 45 amino acid residues. Reference is made to Srisodsuk M. etal., 1993 for a discussion of the linker peptide of T. reesei CBH1.

In addition to the linker sequence, a heterologous exo-endo cellulasefusion construct or expression vector of the invention may include acleavage site, such as a protease cleavage site. In one preferredembodiment, the cleavage site is a kexin site which encodes thedipeptide Lys-Arg.

In a preferred embodiment, the heterologous exo-endo cellulase fusionconstruct and an expression vector including the same will lack the CBDof the CBH. In other embodiments the CBD will be included in theconstruct or vector.

The heterologous exo-endo cellulase fusion constructs include a codingsequence for the catalytic domain of an endoglucanase. Endoglucanasesare found in more than 13 of the Glycosyl Hydrolase families using theclassification of Coutinho, P. M. et al. (1999) Carbohydrate-ActiveEnzymes (CAZy) server at (afmb.cnrs-mrs.fr/-cazy/CAZY/index). Preferablythe catalytic domain is derived from a bacterial endoglucanase. Asdescribed above numerous bacterial endoglucanases are known.

Particularly preferred DNA sequences encoding a catalytic domain of abacterial endoglucanase include:

a) the DNA of SEQ ID NO: 7 encoding an Acidothermus cellulolyticus GH5Aendoglucanase I (E1) catalytic domain having amino acid sequence SEQ IDNO: 8;

b) the DNA of SEQ ID NO: 9 encoding an Acidothermus cellulolyticus GH74endoglucanase catalytic domain having amino acid sequence SEQ ID NO: 10;

c) the DNA of SEQ ID NO: 11 encoding a Thermobifida furca E5endoglucanase having amino acid sequence SEQ ID NO: 12 and

d) DNA sequences or homologous DNA sequences encoding any equivalents ofsaid amino acid sequences of SEQ ID NOs: 8, 10 and 12 wherein saidequivalents have a similar qualitative biological activity to saidsequences.

In some preferred embodiments, the endoglucanase is an Acidothermuscellulolyticus E1 and reference is made to the an Acidothermuscellulolyticus endoglucanases disclosed in WO 9105039; WO 9315186; U.S.Pat. No. 5,275,944; WO 9602551; U.S. Pat. No. 5,536,655 and WO 0070031.Also reference is made to GenBank U33212. In some embodiments, theAcidothermus cellulolyticus E1 has an amino acid sequence of a least90%, 93%, 95% and 98% sequence identity with the sequence set forth inSEQ ID NO: 6.

As stated above homologous nucleic acid sequences to the nucleic acidsequences illustrated in SEQ ID NOs: 1, 3, 7, 9 and 11 may be used in aheterologous cellulase fusion construct or vector according to theinvention. Homologous sequences include sequences found in otherspecies, naturally occurring allelic variants and biologically activefunctional derivatives. A homologous sequence will have at least 80%,85%, 88%, 90%, 93%, 95%, 97%, 98% and 99% identity to one of thesequences of SEQ ID NOs: 1, 3, 7, 9 and 11 when aligned using a sequencealignment program. For example, a homologue of a given sequence hasgreater than 80% sequence identity over a length of the given sequencee.g., the coding sequence for the Tf-E5 catalytic domain as describedherein.

For a given heterologous exo-endo cellulase fusion construct orcomponents of the construct it is appreciated that as a result of thedegeneracy of the genetic code, a number of coding sequences can beproduced that encode a protein having the same amino acid sequence. Forexample, the triplet CGT encodes the amino acid arginine. Arginine isalternatively encoded by CGA, CGC, CGG, AGA, and AGG. Therefore it isappreciated that such substitutions in the coding region fall within thenucleic acid sequences covered by the present invention. Any and all ofthese sequences can be utilized in the same way as described herein fora CBH catalytic domain or a bacterial EG catalytic domain.

Exemplary computer programs which can be used to determine identitybetween two sequences include, but are not limited to, the suite ofBLAST programs, e.g., BLASTN, BLASTX, and TBLASTX, BLASTP and TBLASTN,publicly available on the Internet at www.ncbi.nlm.nih.gov/BLAST/. Seealso, Altschul, et al., 1990 and Altschul, et al., 1997.

Sequence searches are typically carried out using the BLASTN programwhen evaluating a given nucleic acid sequence relative to nucleic acidsequences in the GenBank DNA Sequences and other public databases. TheBLASTX program is preferred for searching nucleic acid sequences thathave been translated in all reading frames against amino acid sequencesin the GenBank Protein Sequences and other public databases. Both BLASTNand BLASTX are run using default parameters of an open gap penalty of11.0, and an extended gap penalty of 1.0, and utilize the BLOSUM-62matrix. (See, e.g., Altschul, et al., 1997.)

A preferred alignment of selected sequences in order to determine “%identity” between two or more sequences, is performed using for example,the CLUSTAL-W program in MacVector version 6.5, operated with defaultparameters, including an open gap penalty of 10.0, an extended gappenalty of 0.1, and a BLOSUM 30 similarity matrix.

In one exemplary approach, sequence extension of a nucleic acid encodinga CBH or EG catalytic domain may be carried out using conventionalprimer extension procedures as described in Sambrook et al., supra, todetect CBH or bacterial EG precursors and processing intermediates ofmRNA that may not have been reverse-transcribed into cDNA and/or toidentify ORFs that encode the catalytic domain or full length protein.

In yet another aspect, the entire or partial nucleotide sequence of thenucleic acid sequence of the T. reesei chbl or GH5a-E1 may be used as aprobe. Such a probe may be used to identify and clone out homologousnucleic acid sequences from related organisms.

Screening of a cDNA or genomic library with the selected probe may beconducted using standard procedures, such as described in Sambrook etal., (1989). Hybridization conditions, including moderate stringency andhigh stringency, are provided in Sambrook et al., supra.

In addition, alignment of amino acid sequences to determine homology oridentity between sequences is also preferably determined by using a“sequence comparison algorithm.” Optimal alignment of sequences forcomparison can be conducted, e.g., by the local homology algorithm ofSmith & Waterman, Adv. Appl. Math. 2:482 (1981), by the homologyalignment algorithm of Needleman & Wunsch, J. Mol. Biol. 48:443 (1970),by the search for similarity method of Pearson & Lipman, Proc. Nat'lAcad. Sci. USA 85:2444 (1988), by computerized implementations of thesealgorithms (GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin GeneticsSoftware Package, Genetics Computer Group, 575 Science Dr., Madison,Wis.), by visual inspection or MOE by Chemical Computing Group, MontrealCanada.

An example of an algorithm that is suitable for determining sequencesimilarity is the BLAST algorithm, which is described in Altschul, etal., J. Mol. Biol. 215:403-410 (1990) and reference is also made toHenikoff & Henikoff, Proc. Natl. Acad. Sci. USA 89:10915 (1989)).Software for performing BLAST analyses is publicly available through theNational Center for Biotechnology Information (<www.ncbi.nlm.nih.gov>).

The heterologous exo-endo cellulase fusion construct according to theinvention may also include a terminator sequence. In some embodimentsthe terminator and the promoter are derived from the same source, forexample a Trichoderma exo-cellobiohydrolase gene. In other embodimentsthe terminator and promoter are derived from different sources. Inpreferred embodiments the terminator is derived from a filamentousfungal source and particular a Trichoderma. Particularly suitableterminators include cbh1 derived from a strain of Trichodermaspecifically T. reesei and the glucoamylase terminator derived fromAspergillus niger or A. awamori (Nunberg et al., 1984 and Boel et al.,1984).

The heterologous exo-endo cellulase fusion construct or a vectorcomprising a fusion construct may also include a selectable marker. Thechoice of the proper selectable marker will depend on the host cell, andappropriate markers for different hosts are well known in the art.Typical selectable marker genes include argB from A. nidulans or T.reesei, amdS from A. nidulans, pyr4 from Neurospora crassa or T. reesei,pyrG from Aspergillus niger or A. nidulans. Markers useful in vectorsystems for transformation of Trichoderma are described in Finkelstein,Chap. 6, in BIOTECHNOLOGY OF FILAMENTOUS FUNGI, Finkelstein et al eds.Butterworth-Heinemann, Boston, Mass. 1992. The amdS gene fromAspergillus nidulans encodes the enzyme acetamidase that allowstransformant cells to grow on acetamide as a nitrogen source (Kelley etal., EMBO J. 4:475-479 (1985) and Penttila et al., Gene 61:155-164(1987)). The selectable marker (e.g. pyrG) may restore the ability of anauxotrophic mutant strain to grow on a selective minimal medium and theselectable marker (e.g. olic31) may confer to transformants the abilityto grow in the presence of an inhibitory drug or antibiotic

A typical heterologous exo-endo cellulase fusion construct is depictedin FIGS. 1 and 10. Methods used to ligate a heterologous exo-endocellulase fusion construct encompassed by the invention and otherheterologous nucleic acid sequences and to insert them into suitablevectors are well known in the art. Linking is generally accomplished byligation at convenient restriction sites, and if such sites do notexist, synthetic oligonucleotide linkers are used in accordance withconventional practice. Additionally vectors can be constructed usingknown recombination techniques.

Any vector may be used as long as it is replicable and viable in thecells into which it is introduced. Large numbers of suitable cloning andexpression vectors are described in Sambrook et al., 1989, Ausubel F Met al., 1993, and Strathern et al., 1981, each of which is expresslyincorporated by reference herein. Further appropriate expression vectorsfor fungi are described in van den Hondel, C. A. M. J. J. et al. (1991)In: Bennett, J. W. and Lasure, L. L. (eds.) More Gene Manipulations inFungi. Academic Press, pp. 396-428. The appropriate DNA sequence may beinserted into a vector by a variety of procedures. In general, the DNAsequence is inserted into an appropriate restriction endonucleasesite(s) by standard procedures. Such procedures and related sub-cloningprocedures are deemed to be within the scope of knowledge of thoseskilled in the art. Exemplary useful plasmids include pUC18, pBR322,pUC100, pSL1180 (Pharmacia Inc., Piscataway, N.J.) and pFB6. Othergeneral purpose vectors such as in Aspergillus, pRAX and in Trichoderma,pTEX maybe also be used (FIGS. 12 and 13).

In one embodiment, a preferred vector is the vector disclosed in FIGS.12 and 13, wherein the vector includes the nucleic acid sequenceencoding the CBD, linker and catalytic domain of the Thermobifida fuscaendoglucanase 5 (SEQ ID NO: 12). In another embodiment, a preferredvector is the vector disclosed in FIGS. 12 and 13, wherein the vectorincludes the nucleotide sequence encoding an Acidothermus cellulolyticusGH5A endoglucanase catalytic domain (SEQ ID NO: 8).

B. Target Host Cells.

In one embodiment of the present invention, the filamentous fungalparent or host cell may be a cell of a species of, but not limited to,Trichoderma sp., Penicillium sp., Humicola sp., Chrysosporium sp.,Gliocladium sp., Aspergillus sp., Fusarium sp., Neurospora sp., Hypocreasp., and Emericella sp. As used herein, the term “Trichoderma” or“Trichoderma sp.” refers to any fungal strains which have previouslybeen classified as Trichoderma or are currently classified asTrichoderma. Some preferred species for Trichoderma fungal parent cellsinclude Trichoderma longibrachiatum (reesei), Trichoderma viride,Trichoderma koningii, and Trichoderma harzianum cells. Particularlypreferred host cells include cells from strains of T. reesei, such asRL-P37 (Sheir-Neiss, et al., Appl. Microbiol. Biotechnol. 20:46-53(1984) and functionally equivalent and derivative strains, such asTrichoderma reesei strain RUT-C30 (ATCC No. 56765) and strain QM9414(ATCC No. 26921). Also reference is made to ATCC No. 13631, ATCC No.26921, ATCC No. 56764, ATCC No. 56767 and NRRL 1509.

Some preferred species for Aspergillus fungal parent cells includeAspergillus niger, Aspergillus awamori, Aspergillus aculeatus, andAspergillus nidulans cells. In one embodiment, the strain comprisesAspergillus niger, for example A. niger var. awamori dgr246 (Goedegebuuret al, (2002) Curr. Genet. 41: 89-98) and GCDAP3, GCDAP4 and GAPS-4(Ward, M, et al., (1993), Appl. Microbiol. Biotechnol. 39:738-743).

In some instances it is desired to obtain a filamentous host cell strainsuch as a Trichoderma host cell strain which has had one or morecellulase genes deleted prior to introduction of a heterologous exo-endocellulase fusion construct encompassed by the invention. Such strainsmay be prepared by the method disclosed in U.S. Pat. No. 5,246,853, U.S.Pat. No. 5,861,271 and WO 92/06209, which disclosures are herebyincorporated by reference. By expressing a cellulase fusion protein orcomponents thereof having cellulolytic activity in a host microorganismthat is missing one or more cellulase genes, the identification andsubsequent purification procedures are simplified. Any gene fromTrichoderma sp. which has been cloned can be deleted, for example, thecbh1, cbh2, egl1, and egl2 genes as well as those encoding EG3 and/orEG5 protein (see e.g., U.S. Pat. No. 5,475,101 and WO 94/28117,respectively). Gene deletion may be accomplished by inserting a form ofthe desired gene to be deleted or disrupted into a plasmid by methodsknown in the art.

Parental fungal cell lines are generally cultured under standardconditions with media containing physiological salts and nutrients, suchas described by Pourquie, J. et al., BIOCHEMISTRY AND GENETICS OFCELLULOSE DEGRADATION, eds. Aubert J. P. et al., Academic Press pp.71-86 (1988) and Ilmen, M. et al., Appl. Environ. Microbiol.63:1298-1306 (1997). Also reference is made to common commerciallyprepared media such as yeast Malt Extract (YM) broth, Luria Bertani (LB)broth and Sabouraud Dextrose (SD) broth.

C. Introduction of a Heterologous Exo-Endo Cellulase Fusion Construct orVector into Fungal Host Cells and Culture Conditions.

A host fungal cell may be genetically modified (i.e., transduced,transformed or transfected) with a heterologous exo-endo cellulasefusion construct according to the invention, a cloning vector or anexpression vector comprising a heterologous exo-endo cellulase fusionconstruct. The methods of transformation of the present invention mayresult in the stable integration of all or part of the construct orvector into the genome of the filamentous fungus. However,transformation resulting in the maintenance of a self-replicatingextra-chromosomal transformation vector is also contemplated.

Many standard transformation methods can be used to produce afilamentous fungal cell line such as a Trichoderma or Aspergillus cellline that express large quantities of a heterologous protein. Some ofthe published methods for the introduction of DNA constructs intocellulase-producing strains of Trichoderma include Lorito, Hayes,DiPietro and Harman (1993) Curr. Genet. 24: 349-356; Goldman, VanMontaguand Herrera-Estrella (1990) Curr. Genet. 17:169-174; Penttila,Nevalainen, Ratto, Salminen and Knowles (1987) Gene 61: 155-164, EP-A-0244 234 and also Hazell B. et al., 2000; for Aspergillus include Yelton,Hamer and Timberlake (1984) Proc. Natl. Acad. Sci. USA 81: 1470-1474;for Fusarium include Bajar, Podila and Kolattukudy, (1991) Proc. Natl.Acad. Sci. USA 88: 8202-8212; for Streptomyces include Hopwood et al.,(1985) Genetic Manipulation of Streptomyces: A Laboratory Manual, TheJohn Innes Foundation, Norwich, UK; and for Bacillus include Brigidi,DeRossi, Bertarini, Riccardi and Matteuzzi, (1990), FEMS Microbiol.Lett. 55: 135-138.

Other methods for introducing a heterologous exo-endo cellulase fusionconstruct or vector into filamentous fungi (e.g., H. jecorina) include,but are not limited to the use of a particle or gene gun (biolistics),permeabilization of filamentous fungi cells walls prior to thetransformation process (e.g., by use of high concentrations of alkali,e.g., 0.05 M to 0.4 M CaCl₂ or lithium acetate), protoplast fusion,electroporation, or agrobacterium mediated transformation (U.S. Pat. No.6,255,115).

An exemplary method for transformation of filamentous fungi by treatmentof protoplasts or spheroplasts with polyethylene glycol and CaCl₂ isdescribed in Campbell, et al., (1989) Curr. Genet. 16:53-56, 1989 andPenttila, M. et al., (1988) Gene, 63:11-22 and Penttila, M. et al.,(1987) Gene 61:155-164.

Any of the well-known procedures for introducing foreign nucleotidesequences into host cells may be used. It is only necessary that theparticular genetic engineering procedure used be capable of successfullyintroducing at least one gene into the host cell capable of expressingthe heterologous gene.

The invention includes the transformants of filamentous fungi especiallyTrichoderma cells comprising the coding sequences for the cellulasefusion protein. The invention further includes the filamentous fungitransformants for use in producing fungal cellulase compositions, whichinclude the cellulase fusion protein or components thereof.

Following introduction of a heterologous exo-endo cellulase fusionconstruct comprising the exoglucanase catalytic domain coding sequenceand the endoglucanase catalytic domain coding sequence, the geneticallymodified cells can be cultured in conventional nutrient media asdescribed above for growth of target host cells and modified asappropriate for activating promoters and selecting transformants. Theculture conditions, such as temperature, pH and the like, are thosepreviously used for the host cell selected for expression, and will beapparent to those skilled in the art. Also preferred culture conditionsfor a given filamentous fungus may be found in the scientific literatureand/or from the source of the fungi such as the American Type CultureCollection (ATCC; www.atcc.org/).

Stable transformants of filamentous fungi can generally be distinguishedfrom unstable transformants by their faster growth rate and theformation of circular colonies with a smooth rather than ragged outlineon solid culture medium. Additionally, in some cases, a further test ofstability can be made by growing the transformants on solidnon-selective medium, harvesting the spores from this culture medium anddetermining the percentage of these spores which will subsequentlygerminate and grow on selective medium.

The progeny of cells into which such heterologous exo-endo cellulasefusion constructs, or vectors including the same, have been introducedare generally considered to comprise the fusion protein encoded by thenucleic acid sequence found in the heterologous cellulase fusionconstruct.

In one exemplary application of the invention encompassed herein arecombinant strain of filamentous fungi, e.g., Trichoderma reesei,comprising a heterologous exo-endo cellulase fusion construct willproduce not only a cellulase fusion protein but also will producecomponents of the cellulase fusion protein. In some embodiments therecombinant cells including the cellulase fusion construct will producean increased amount of cellulolytic activity compared to a correspondingrecombinant filamentous fungi strain grown under essentially the sameconditions but genetically modified to include separate heterologousnucleic acid constructs encoding an exo-cellobiohydrolase catalyticdomain and/or an endoglucanase catalytic domain.

D. Analysis of Protein Expression

In order to evaluate the expression of a cellulase fusion protein of theinvention by a cell line that has been transformed with a heterologousexo-endo cellulase fusion construct, assays can be carried out at theprotein level, the RNA level or by use of functional bioassaysparticular to exo-cellobiohydrolase activity or endoglucanase activityand/or production.

In general, the following assays can be used to determine integration ofcellulase fusion protein expression constructs and vector sequences,Northern blotting, dot blotting (DNA or RNA analysis), RT-PCR (reversetranscriptase polymerase chain reaction), in situ hybridization, usingan appropriately labeled probe (based on the nucleic acid codingsequence), conventional Southern blotting and autoradiography.

In addition, the production and/or expression of a cellulase enzyme maybe measured in a sample directly, for example, by assays forcellobiohydrolase or endoglucanase activity, expression and/orproduction. Such assays are described, for example, in Becker et al.,Biochem J. (2001) 356:19-30; Mitsuishi et al., FEBS (1990) 275:135-138.Shoemaker et al. 1978; and Schulein 1988) each of which is expresslyincorporated by reference herein. The ability of CBH1 to hydrolyzeisolated soluble and insoluble substrates can be measured using assaysdescribed in Srisodsuk et al., J. Biotech. (1997) 57:49-57 and Nidetzkyand Claeyssens Biotech. Bioeng. (1994) 44:961-966. Substrates useful forassaying exo-cellobiohydrolase, endoglucanase or β-glucosidaseactivities include crystalline cellulose, filter paper, phosphoric acidswollen cellulose, cellooligosaccharides, methylumbelliferyl lactoside,methylumbelliferyl cellobioside, orthonitrophenyl lactoside,paranitrophenyl lactoside, orthonitrophenyl cellobioside,paranitrophenyl cellobioside.

In addition, protein expression, may be evaluated by immunologicalmethods, such as immunohistochemical staining of cells, tissue sectionsor immunoassay of tissue culture medium, e.g., by Western blot or ELISA.Such immunoassays can be used to qualitatively and quantitativelyevaluate expression of a cellulase, for example CBH. The details of suchmethods are known to those of skill in the art and many reagents forpracticing such methods are commercially available.

In an embodiment of the invention, the cellulase fusion protein which isexpressed by the recombinant host cell will be about 0.1 to 80% of thetotal expressed cellulase. In other embodiments, the amount of expressedfusion protein will be in the range of about 0.1 mg to 100 g; about 0.1mg to 50 g and 0.1 mg to 10 g protein per liter of culture media.

E. Recovery and Purification of Cellulase Fusion Proteins and ComponentsThereof.

In general, a cellulase fusion protein or components of the cellulasefusion protein produced in cell culture are secreted into the medium andmay be recovered and optionally purified, e.g., by removing unwantedcomponents from the cell culture medium. However, in some cases, acellulase fusion protein or components thereof may be produced in acellular form necessitating recovery from a cell lysate. In such casesthe protein is purified from the cells in which it was produced usingtechniques routinely employed by those of skill in the art. Examplesinclude, but are not limited to, affinity chromatography (van Tilbeurghet al., FEBS Lett. 16:215, 1984), ion-exchange chromatographic methods(Goyal et al., Bioresource Technol. 36:37-50, 1991; Fliess et al., Eur.J. Appl. Microbiol. Biotechnol. 17:314-318, 1983; Bhikhabhai et al., J.Appl. Biochem. 6:336-345, 1984; Ellouz et al., J. Chromatography396:307-317, 1987), including ion-exchange using materials with highresolution power (Medve et al., J. Chromatography A 808:153-165, 1998),hydrophobic interaction chromatography (Tomaz and Queiroz, J.Chromatography A 865:123-128, 1999), and two-phase partitioning(Brumbauer, et al., Bioseparation 7:287-295, 1999).

Once expression of a given cellulase fusion protein is achieved, theproteins thereby produced may be purified from the cells or cell cultureby methods known in the art and reference is made to Deutscher, Methodsin Enzymology, vol. 182, no. 57, pp. 779, 1990; and Scopes, MethodsEnzymol. 90: 479-91, 1982. Exemplary procedures suitable for suchpurification include the following: antibody-affinity columnchromatography, ion exchange chromatography; ethanol precipitation;reverse phase HPLC; chromatography on silica or on a cation-exchangeresin such as DEAE; chromatofocusing; SDS-PAGE; ammonium sulfateprecipitation; and gel filtration using, e.g., Sephadex G-75.

A purified form of a cellulase fusion protein or components thereof maybe used to produce either monoclonal or polyclonal antibodies specificto the expressed protein for use in various immunoassays. (See, e.g., Huet al., Mol Cell Biol. vol. 11, no. 11, pp. 5792-5799, 1991). Exemplaryassays include ELISA, competitive immunoassays, radioimmunoassays,Western blot, indirect immunofluorescent assays and the like.

F. Utility of Enzymatic Compositions Comprising the Cellulase FusionProteins or Components Thereof.

The cellulase fusion protein and components comprising the catalyticdomains of the cellulase fusion protein find utility in a wide varietyapplications, including use in detergent compositions, stonewashingcompositions, in compositions for degrading wood pulp into sugars (e.g.,for bio-ethanol production), and/or in feed compositions. In someembodiments, the cellulase fusion protein or components thereof may beused as cell free extracts. In other embodiments, the fungal cellsexpressing a heterologous exo-endo cellulase fusion construct are grownunder batch or continuous fermentation conditions. A classical batchfermentation is a closed system, wherein the composition of the mediumis set at the beginning of the fermentation and is not subject toartificial alterations during the fermentation. Thus, at the beginningof the fermentation the medium is inoculated with the desiredorganism(s). In this method, fermentation is permitted to occur withoutthe addition of any components to the system. Typically, a batchfermentation qualifies as a “batch” with respect to the addition of thecarbon source and attempts are often made at controlling factors such aspH and oxygen concentration. The metabolite and biomass compositions ofthe batch system change constantly up to the time the fermentation isstopped. Within batch cultures, cells progress through a static lagphase to a high growth log phase and finally to a stationary phase wheregrowth rate is diminished or halted. If untreated, cells in thestationary phase eventually die. In general, cells in log phase areresponsible for the bulk of production of end product.

A variation on the standard batch system is the “fed-batch fermentation”system, which also finds use with the present invention. In thisvariation of a typical batch system, the substrate is added inincrements as the fermentation progresses. Fed-batch systems are usefulwhen catabolite repression is apt to inhibit the production of productsand where it is desirable to have limited amounts of substrate in themedium. Measurement of the actual substrate concentration in fed-batchsystems is difficult and is therefore estimated on the basis of thechanges of measurable factors such as pH, dissolved oxygen and thepartial pressure of waste gases such as CO₂. Batch and fed-batchfermentations are common and well known in the art.

Continuous fermentation is an open system where a defined fermentationmedium is added continuously to a bioreactor and an equal amount ofconditioned medium is removed simultaneously for processing. Continuousfermentation generally maintains the cultures at a constant high densitywhere cells are primarily in log phase growth.

Continuous fermentation allows for the modulation of one factor or anynumber of factors that affect cell growth and/or end productconcentration. For example, in one embodiment, a limiting nutrient suchas the carbon source or nitrogen source is maintained at a fixed rate anall other parameters are allowed to moderate. In other systems, a numberof factors affecting growth can be altered continuously while the cellconcentration, measured by media turbidity, is kept constant. Continuoussystems strive to maintain steady state growth conditions. Thus, cellloss due to medium being drawn off must be balanced against the cellgrowth rate in the fermentation. Methods of modulating nutrients andgrowth factors for continuous fermentation processes as well astechniques for maximizing the rate of product formation are well knownin the art of industrial microbiology.

In some applications, the cellulase fusion protein and componentsthereof find utility in detergent compositions, stonewashingcompositions or in the treatment of fabrics to improve their feel andappearance. A detergent composition refers to a mixture which isintended for use in a wash medium for the laundering of soiled cellulosecontaining fabrics. A stonewashing composition refers to a formulationfor use in stonewashing cellulose containing fabrics. Stonewashingcompositions are used to modify cellulose containing fabrics prior tosale, i.e., during the manufacturing process. In contrast, detergentcompositions are intended for the cleaning of soiled garments and arenot used during the manufacturing process.

In the context of the present invention, such compositions may alsoinclude, in addition to cellulases, surfactants, additional hydrolyticenzymes, builders, bleaching agents, bleach activators, bluing agentsand fluorescent dyes, caking inhibitors, masking agents, cellulaseactivators, antioxidants, and solubilizers.

Surfactants may comprise anionic, cationic and nonionic surfactants suchas those commonly found in detergents. Anionic surfactants includelinear or branched alkylbenzenesulfonates; alkyl or alkenyl ethersulfates having linear or branched alkyl groups or alkenyl groups; alkylor alkenyl sulfates; olefinsulfonates; and alkanesulfonates. Ampholyticsurfactants include quaternary ammonium salt sulfonates, andbetaine-type ampholytic surfactants. Such ampholytic surfactants haveboth the positive and negative charged groups in the same molecule.Nonionic surfactants may comprise polyoxyalkylene ethers, as well ashigher fatty acid alkanolamides or alkylene oxide adduct thereof, fattyacid glycerine monoesters, and the like.

Cellulose containing fabric may be any sewn or unsewn fabrics, yarns orfibers made of cotton or non-cotton containing cellulose or cotton ornon-cotton containing cellulose blends including natural cellulosics andmanmade cellulosics (such as jute, flax, ramie, rayon, and lyocell).Cotton-containing fabrics are sewn or unsewn fabrics, yarns or fibersmade of pure cotton or cotton blends including cotton woven fabrics,cotton knits, cotton denims, cotton yarns, raw cotton and the like.

Preferably the cellulase compositions comprising the cellulase fusionprotein or components thereof are employed from about 0.00005 weightpercent to about 5 weight percent relative to the total detergentcomposition. More preferably, the cellulase compositions are employedfrom about 0.0002 weight percent to about 2 weight percent relative tothe total detergent composition.

Since the rate of hydrolysis of cellulosic products may be increased byusing a transformant having a heterologous cellulase fusion constructinserted into the genome, products that contain cellulose orheteroglycans can be degraded at a faster rate and to a greater extent.Products made from cellulose such as paper, cotton, cellulosic diapersand the like can be degraded more efficiently in a landfill. Thus, thefermentation product obtainable from the transformants or thetransformants alone may be used in compositions to help degrade byliquefaction a variety of cellulose products that add to the overcrowdedlandfills.

Cellulose-based feedstocks are comprised of agricultural wastes, grassesand woods and other low-value biomass such as municipal waste (e.g.,recycled paper, yard clippings, etc.). Ethanol may be produced from thefermentation of any of these cellulosic feedstocks. However, thecellulose must first be converted to sugars before there can beconversion to ethanol. A composition containing an enhanced amount ofcellulolytic activity due to the inclusion of a cellulase fusion proteinor components thereof may find utility in ethanol production

Ethanol can be produced via saccharification and fermentation processesfrom cellulosic biomass such as trees, herbaceous plants, municipalsolid waste and agricultural and forestry residues. However, the ratioof individual cellulase enzymes within a naturally occurring cellulasemixture produced by a microbe may not be the most efficient for rapidconversion of cellulose in biomass to glucose. It is known thatendoglucanases act to produce new cellulose chain ends which themselvesare substrates for the action of cellobiohydrolases and thereby improvethe efficiency of hydrolysis of the entire cellulase system. Therefore,the use of increased or optimized endoglucanase activity from acellulase fusion protein or components thereof may greatly enhance theproduction of ethanol and sugar which can be converted by fermentationto other chemicals.

Thus, the inventive cellulase fusion protein and components thereof finduse in the hydrolysis of cellulose to its sugar components. In oneembodiment, the cellulase fusion protein or components thereof are addedto the biomass prior to the addition of a fermentative organism. Inanother embodiment, the cellulase fusion protein or components thereofare added to the biomass at the same time as a fermentative organism.Optionally, there may be other cellulase components present in eitherembodiment.

EXPERIMENTAL

The present invention is described in further detail in the followingexamples which are not in any way intended to limit the scope of theinvention.

In the disclosure and experimental section, which follows, the followingabbreviations apply:

CBH1-E1 (T. reesei CBH1 catalytic domain and linker fused to anAcidothermus cellulolyticus GH5A endoglucanase I catalytic domain);

CBH1-74E (T. reesei CBH1 catalytic domain and linker fused to anAcidothermus cellulolyticus GH74 endoglucanase catalytic domain);

CBH1-TfE5 (T. reesei CBH1 catalytic domain and linker fused to aThermobifida fusca E5 endoglucanase cellulose binding domain, linker andThermobifida fusca E5 endoglucanase catalytic domain;

wt % (weight percent); ° C. (degrees Centigrade); rpm (revolutions perminute); H₂O (water); dH₂O (deionized water); aa (amino acid); by (basepair); kb (kilobase pair); kD (kilodaltons); g (grams); μg (micrograms);mg (milligrams); μL (microliters); ml and mL (milliliters); mm(millimeters); μm (micrometer); M (molar); mM (millimolar); μM(micromolar); U (units); MW (molecular weight); sec (seconds); min(s)(minute/minutes); hr(s) (hour/hours); PAGE (polyacrylamide gelelectrophoresis); phthalate buffer, (sodium phthalate in water, 20 mN,pH 5.0); PBS (phosphate buffered saline [150 mM NaCl, 10 mM sodiumphosphate buffer, pH 7.2]); SDS (sodium dodecyl sulfate); Tris(tris(hydroxymethyl)aminomethane); w/v (weight to volume); w/w (weightto weight); v/v (volume to volume); and Genencor (GenencorInternational, Inc., Palo Alto, Calif.).

Example 1 Construction of a CBH1-E1 Fusion Vector

The CBH1-E1 fusion construct included the T. reesei cbh1 promoter; theT. reesei cbh1 gene sequence from the start codon to the end of the cbh1linker and an additional 12 bases of DNA 5′ to the start of theendoglucanase coding sequence, a stop codon and the T. reesei cbh1terminator (see FIGS. 10 and 11). The additional 12 DNA bases(ACTAGTAAGCGG)) (SEQ ID NO. 16) code for the restriction endonucleaseSpeI and the amino acids Ser, Lys, and Arg.

The plasmid E1-pUC19 which contained the open reading frame for the E1gene locus was used as the DNA template in a PCR reaction. (Equivalentplasmids are described in U.S. Pat. No. 5,536,655, which describescloning the E1 gene from the actinomycete Acidothermus cellulolyticusATCC 43068, Mohagheghi A. et al., 1986).

Standard procedures for working with plasmid DNA and amplification ofDNA using the polymerase chain reaction (PCR) are found in Sambrook, etal., 2001.

The following two primers were used to amplify the coding region of thecatalytic domain of the E1 endoglucanase.

Forward Primer 1 = EL-316 (containing a SpeI site): (SEQ ID NO: 17)GCTTATACTAGTAAGCGCGCGGGCGGCGGCTATTGGCACAC Reverse Primer 2 =EL-317 (containing an AscI site and stop codon-reverse compliment):(SEQ ID NO: 18) GCTTATGGCGCGCC TTAGACAGGATCGAAAATCGACGAC.

The reaction conditions were as follows using materials from thePLATINUM Pfx DNA Polymerase kit (Invitrogen, Carlsbad, Calif.): 1 μldNTP Master Mix (final concentration 0.2 mM); 1 μl primer 1 (final conc0.5 μM); 1 μl primer 2 (final conc 0.5 μM); 2 μl DNA template (finalconc 50-200 ng); 1 μl 50 mM MgSO₄ (final conc 1 mM); 5 μl 10×PfxAmplification Buffer; 5 μl 10×PCRx Enhancer Solution; 1 μl Platinum PfxDNA Polymerase (2.5 U total); 33 μl water for 50 μl total reactionvolume.

Amplification parameters were: step 1—94° C. for 2 min (1st cycle onlyto denature antibody bound polymerase); step 2—94° C. for 45 sec; step3—60° C. for 30 sec; step 4—68° C. for 2 min; step 5—repeated step 2 for24 cycles and step 6—68° C. for 4 min.

The appropriately sized PCR product was cloned into the Zero Blunt TOPOvector and transformed into chemically competent Top10 E. coli cells(Invitrogen Corp., Carlsbad, Calif.)—plated onto to appropriateselection media (LA with 50 ppm with kanamycin and grown overnight at37° C. Several colonies were picked from the plate media and grownovernight in 5 ml cultures at 37° C. in selection media (LB with 50 ppmkanamycin) from which plasmid mini-preps were made. Plasmid DNA fromseveral clones was restriction digested to confirm the correct sizeinsert. The correct sequence was confirmed by DNA sequencing. Followingsequence verification, the E1 catalytic domain was excised from the TOPOvector by digesting with the restriction enzymes SpeI and AscI. Thisfragment was ligated into the pTrex4 vector which had been digested withthe restriction enzymes SpeI and AscI (see, FIGS. 12 and 13).

The ligation mixture was transformed into MM294 competent E. coli cells,plated onto appropriate selection media (LA with 50 ppm carbenicillin)and grown overnight at 37° C. Several colonies were picked from theplate media and grown overnight in 5 ml cultures at 37° C. in selectionmedia (LA with 50 ppm carbenicillin) from which plasmid mini-preps weremade. Correctly ligated CBH1-E1 fusion protein vectors were confirmed byrestriction digestion.

Example 2 Transformation and Expression the CBH1-E1 Fusion Constructinto a T. reesei Host Strain

Various T. reesei strains were transformed with the CBH1-E1 fusionconstruct. The host strains included a derivative of T. reesei R^(L)—P37and a derivative of T. reesei wherein the native cellulase genes (cbh1,cbh2, egl1 and egl2) were deleted.

Approximately one-half swab (or 1-2 cm²) of a plate of a sporulated T.reesei derivative of strain RL-P37 (Sheir-Neiss, et al., 1984) mycelia(grown on a PDA plate for 7 days at 28° C.) was inoculated into 50 ml ofYEG (5 g/L yeast extract plus 20 g/L glucose) broth in a 250 ml,4-baffled shake flask and incubated at 30° C. for 16-20 hours at 200rpm. The mycelia was recovered by transferring the liquid volume into 50ml conical tubes and spinning at 2500 rpm for 10 minutes. Thesupernatant was aspirated off. The mycelial pellet was transferred intoa 250 ml, CA Corning bottle containing 40 ml of B glucanase solution andincubated at 30° C., 200 rpm for 2 hrs to generate protoplasts fortransformation. Protoplasts were harvested by filtration through sterilemiracloth into a 50 ml conical tube. They were pelleted by spinning at2000 rpm for 5 minutes, the supernate was aspirated off. The protoplastpellet was washed once with 50 ml of 1.2 M sorbitol, spun down,aspirated, and washed with 25 ml of sorbitol CaCl₂. Protoplasts werecounted and then pelleted again at 2000 rpm for 5 min, the supernate wasaspirated off, and the protoplast pellet was resuspended in a sufficientvolume of sorbitol/CaCl₂ to generate a protoplast concentration of1.25×10⁸ protoplasts per ml. This constitutes the protoplast solution.

Aliquots of up to 20 μg of expression vector DNA (in a volume no greaterthan 20 μl) were placed into 15 ml conical tubes and the tubes were puton ice. Then 200 μl of the protoplast solution was added, followed by 50μl PEG solution to each transformation aliquot. The tubes were mixedgently and incubated on ice for 20 min. Next, an additional 2 ml of PEGsolution was added to the transformation aliquot tubes, followed bygentle inversion and incubation at room temperature for 5 minutes. Next4 ml of Sorbitol/CaCl₂ solution was added to the tubes (generating atotal volume of 6.2 ml). This transformation mixture was divided into 3aliquots each containing about 2 ml. An overlay mixture was created byadding each of these three aliquots to three tubes containing 10 ml ofmelted acetamide/sorbitol top agar (kept molten by holding at 50° C.)and this overlay mixture was poured onto a selection plate ofacetamide/sorbitol agar. The transformation plates were then incubatedat 30° C. for four to seven days.

The transformation was performed with amdS selection. Acetamide/sorbitolplates and overlays were used for the transformation. For the selectionplates, the same plates were used, but without sorbitol. Transformantswere purified by transfer of isolated colonies to fresh selective mediacontaining acetamide.

With reference to the examples the following solutions were made asfollows.

1) 40 ml β-D-glucanase solution was made up in 1.2M sorbitol andincluded 600 mg β-D-glucanase and 400 mg MgSO₄.7H₂O (Catalog No. 0439-1,InterSpex Products Inc., San Mateo, Calif.).

2) 200 ml PEG solution contained 50 g polyethylene glycol 4000 (BDHLaboratory Supplies Poole, England) and 1.47 g CaCl₂-2H₂O made up indH₂O.

3) Sorbitol/CaCl₂ contained 1.2M sorbitol and 50 mM CaCl₂.

4) Acetamide/sorbitol agar:

-   -   Part 1—0.6 g acetamide (Aldrich, 99% sublime.), 1.68 g CsCl, 20        g glucose, 20 g KH₂PO₄, 0.6 g MgSO₄.7H₂O, 0.6 g CaCl₂-2H₂O, 1 ml        1000× salts (see below), adjusted to pH 5.5, brought to volume        (300 mls) with dH₂O, filtered and sterilized.    -   Part II—20 g Noble agar and 218 g sorbitol brought to volume        (700 mls) with dH₂O and autoclaved.    -   Part II was added to part I for a final volume of 1 L.

5) 1000× Salts—5 g FeSO₄.7H₂O, 1.6 g MnSO₄.H₂O, 1.4 g ZnSO₄.7H₂O, 1 gCoCl₂.6H₂O were combined and the volume was brought to 1 L with dH₂O.The solution was filtered and sterilized.

6) Acetamide/sorbitol top agar is prepared as is acetamide/sorbitol agarexcept that top agar is substituted for noble agar.

The transformation procedure used was similar to that described inPenttila et al., Gene 61: 155-164, 1987.

Individual fungal transformants were grown up in shake flask culture todetermine the level of fusion protein expression. The experiments wereconducted essentially as described in example 1 of U.S. Pat. No.5,874,276 with the following modification: 16 g/L of alpha-lactose wassubstituted for cellulose in TSF medium. The highest level of cleaved E1protein expression from a transformant in shake flasks was estimated tobe greater than 3 g/L.

In general, the fermentation protocol as described in Foreman et al.(Foreman et al. (2003) J. Biol. Chem. 278:31988-31997) was followed.Vogels minimal medium (Davis et al., (1970) Methods in Enzymology 17A,pg 79-143 and Davis, Rowland, NEUROSPORA, CONTRIBUTIONS OF A MODELORGANISM, Oxford University Press, (2000)) containing 5% glucose wasinoculated with 1.5 ml frozen spore suspension. After 48 hours, eachculture was transferred to 6.2 L of the same medium in a 14 L Biolafittefermenter. The fermenter was run at 25° C., 750 RPM and 8 standardliters per minute airflow. One hour after the initial glucose wasexhausted, a 25% (w/w) lactose feed was started and fed in a carbonlimiting fashion to prevent lactose accumulation. The concentrations ofglucose and lactose were monitored using a glucose oxidase assay kit ora glucose hexokinase assay kit with beta-galactosidase added to cleavelactose, respectively (Instrumentation Laboratory Co., Lexington,Mass.). Samples were obtained at regular intervals to monitor theprogress of the fermentation. Collected samples were spun in a 50 mlcentrifuge tube at ¾ speed in an International Equipment Company(Needham Heights, Mass.) clinical centrifuge.

Shake flask grown supernatant samples were run on BIS-TRIS SDS-PAGE gels(Invitrogen), under reducing conditions with MOPS(morpholinepropanesulfonic acid) SDS running buffer and LDS samplebuffer. The results are provided in FIG. 14.

Example 3 Assay of Cellulolytic Activity from Transformed Trichodermareesei Clones

The following assays and substrates were used to determine thecellulolytic activity of the CBH1-E1 fusion protein.

Pretreated corn stover (PCS)—Corn stover was pretreated with 2% w/wH₂SO₄ as described in Schell, D. et al., J. Appl. Biochem. Biotechnol.105:69-86 (2003) and followed by multiple washes with deionized water toobtain a pH of 4.5. Sodium acetate was added to make a finalconcentration of 50 mM and this was titrated to pH 5.0.Measurement of Total Protein—Protein concentration was measured usingthe bicinchoninic acid method with bovine serum albumin as a standard.(Smith P. K. et al., Biochem 150:76-85, 1985).Cellulose conversion (Soluble sugar determinations) was evaluated byHPLC according to the methods described in Baker et al., Appl. Biochem.Biotechnol. 70-72:395-403 (1998).

A standard cellulosic conversion assay was used in the experiments. Inthis assay enzyme and buffered substrate were placed in containers andincubated at a temperature over time. The reaction was quenched withenough 100 mM Glycine, pH 11.0 to bring the pH of the reaction mixtureto at least pH10. Once the reaction was quenched, an aliquot of thereaction mixture was filtered through a 0.2 micron membrane to removesolids. The filtered solution was then assayed for soluble sugars byHPLC as described above. The cellulose concentration in the reactionmixture was approximately 7%. The enzyme or enzyme mixtures were dosedanywhere from 1 to 60 mg of total protein per gram of cellulose.

In one set of experiments the percent conversion of 13.8% PCS (7.06%cellulose) at 55° C. for 1 day was evaluated using 10 mg enzyme/gcellulose in 50 mM acetate buffer at 55° C. Samples were agitated at 700rpm. Comparisons were made between supernatants from growth of 1) a T.reesei parent strain which included the native cellulase genes and 2) acorresponding T. reesei CBH1-E1 fusion strain transformed according tothe examples herein. The amount of E1 protein expressed by this strainwas 10% w/w (estimated by PAGE as a percent of total protein). Sampleswere quenched at various times up to 24 hours.

The results are presented in FIG. 17, and it is observed that theCBH1-E1 fusion protein outperforms the parent. It took about 6 hours forthe CBH1-E1 fusion protein to yield 20% cellulose conversion, while itrequires 10 hours for the parent cellulase to reach 20% hydrolysis.

Example 4 Transformation and Expression the CBH1-74E Fusion Constructinto T. reesei

The CBH1-74E fusion construct was designed according to the proceduresdescribed above in example 1 with the following differences. The forwardprimer was designed to maintain the reading frame translation andincluded a Lys-Arg kexin cleavage site (underlined). The reverse primerencodes a stop codon (the reverse compliment) at the end of thecatalytic domain.

Primers were ordered with 5 prime phosphates to enable subsequent bluntcloning. The GH74 catalytic domain was amplified with the followingforward and reverse primers:

GH74 forward primer bluntF4- (SEQ ID NO: 19)CTAAGAGAGCGACGACTCAGCCGTACACCTGGAGCAACGTGGC andGH74 reverse primer bluntR4- (SEQ ID NO: 20)TTACGATCCGGACGGCGCACCACCAATGTCCCCGTATA.

Amplification was performed using Stratagene's Herculase High FidelityPolymerase (Stratagene, La Jolla, Calif.). The amplification conditionsfor the GH74 catalytic domain were:

An isolated fragment of DNA encompassing the GH74 catalytic domain wasused as the template for PCR (approximately 0.2 ug of DNA). U.S. Pat.Appln. No. 20030108988 describes the cloning of GH74. (GH74 is referredto as Avilll in the published patent application).

Reaction set up (in ul):

COMPONENT 10X Herculase Buffer 5 10 mM dNTPs 1.5 H₂O 39.5 Fwd primer (10μM) 1 Rev primer (10 μM) 1 Template 1 Herculase Polymerase (5U) 1 Totalreaction volume 50

Cycling:

Segment No. of cycles Temp ° C. hr:min:sec 1 1 95 00:03:00 2 10 9500:00:40 60 00:00:30 72 150 sec 3 20 95 00:00:40 60 00:00:30 72 150sec + 10 sec/cycle 4 1 4 hold

All PCR products were gel purified and treated with Mung Bean Nucleaseto produce blunt ends prior to ligation. The amplified, blunted fragmentwas ligated into pTrex4 vector that had been digested with therestriction enzymes SpeI and AscI followed by nuclease digestion toremove the 3′ overhangs thereby creating blunt ends. The newly createdvector was then transformed into E. coli. Plasmid DNA was isolated fromcolonies of transformed E. coli. Since the amplified GH74 fragment couldinsert into pTrex4 in two different orientations, restriction digestswere performed to discern clones with correctly oriented insert.Putative clones were confirmed by DNA sequencing.

Transformation of the fusion vector into T. reesei was performed usingbiolistic transformation according to the teaching of Hazell, B. W. etal., Lett. Appl. Microbiol. 30:282-286 (2000).

Expression of the CBH1-74E fusion protein was determined as describedabove for expression of the CBH1-E1 fusion protein in Example 2. Thehighest level of cleaved GH74 protein expression from a transformant inshake flasks was estimated to be greater then 3 g/L.

Shake flask grown supernatant samples were run on BIS-TRIS SDS-PAGE gels(Invitrogen), under reducing conditions with MOPS(morpholinepropanesulfonic acid) SDS running buffer and LDS samplebuffer. The results are provided in FIG. 15.

Example 5

Transformation and Expression the CBHI-TfE5 Fusion Construct into T.reesei

The CBH1-TfE5 fusion construct was designed according to the proceduresdescribed above in example 1 with the following differences. A plasmidequivalent to that described in Collmer & Wilson, Bio/technol. 1:594-601 (1983) carrying the TfE5 gene was used as the DNA template toamplify the TfE5. The following primers were used to amplify the TfE5endoglucanase

EL-308 (which contains a SpeI site)-forward primer- (SEQ ID NO: 21)GCTTATACTAGTAAGCGCGCCGGTCTCACCGCCACAGTCACC andEL-309 (which contains a AscI site) reverse primer- (SEQ ID NO: 22)GCTTATGGCGCGCCTCAGGACTGGAGCTTGCTCCGC.

Transformation was as described in example 2 above. The highest level ofcleaved TfE5 protein expression from a transformant in shake flasks wasestimated to be greater than 2 g/L.

Shake flask grown supernatant samples were run on BIS-TRIS SDS-PAGE gels(Invitrogen), under reducing conditions with MOPS(morpholinepropanesulfonic acid) SDS running buffer and LDS samplebuffer. The results are provided in FIG. 16.

REFERENCES

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1. A heterologous exo-endo cellulase fusion construct comprising inoperable linkage from the 5′ end of said molecule a. a DNA moleculeencoding a signal sequence; b. a DNA molecule encoding a catalyticdomain of an exo-cellobiohydrolase; and c. a DNA molecule encoding anendoglucanase catalytic domain.
 2. The heterologous exo-endo cellulasefusion construct according to claim 1 further comprising a linkersequence located 3′ of the catalytic domain of the exo-cellobiohydrolaseand 5′ of the catalytic domain of the endoglucanase.
 3. The heterologousexo-endo cellulase fusion construct according to claim 1 furthercomprising a kexin site located after the linker sequence and before thecoding region of the endoglucanase catalytic domain.
 4. The heterologousexo-endo fusion construct according to claim 1 further comprising apromoter of a filamentous fungus secretable protein, said promoterlocated in operable linkage 5′ of the coding region of theexo-cellobiohydrolase catalytic domain.
 5. The heterologous exo-endofusion construct according to claim 4 wherein the promoter is a cbhpromoter.
 6. The heterologous exo-endo fusion construct according toclaim 5 wherein the promoter is a cbh1 promoter derived from T. reesei.7. The heterologous exo-endo fusion construct according to claim 1wherein the exo-cellobiohydrolase is a CBH1.
 8. The heterologousexo-endo fusion construct according to claim 7 wherein said CBH1comprises an amino acid sequence of at least 90% sequence identity withthe sequence set forth in SEQ ID NO.:
 6. 9. The heterologous exo-endofusion construct according to claim 1 wherein the endoglucanasecatalytic domain is derived from a bacterial endoglucanase.
 10. Theheterologous exo-endo fusion construct according to claim 9 wherein thebacterial endoglucanase catalytic domain is selected from the groupconsisting of an Acidothermus cellulolyticus GH5A endoglucanase I (E1)catalytic domain; an Acidothermus cellulolyticus GH74 endoglucanase(GH74-EG) catalytic domain: and a Thermobifida fusca E5 endoglucanase(Tf-E5) catalytic domain.
 11. The heterologous exo-endo fusion constructaccording to claim 10 wherein the endoglucanase is an Acidothermuscellulolyticus GH5A E1 catalytic domain.
 12. The heterologous exo-endofusion construct according to claim 10 wherein the Acidothermuscellulolyticus GH5A E1 catalytic domain having an amino acid sequence ofat least 90% sequence identity with the sequence set forth in SEQ ID NO.8.
 13. The heterologous exo-endo fusion construct according to claim 1further comprising a terminator sequence located 3′ to the endoglucanasecatalytic domain.
 14. The heterologous exo-endo fusion constructaccording to claim 1 further comprising a selectable marker.
 15. Avector comprising in operable linkage a promoter of a filamentous fungussecretable protein, a DNA molecule encoding a signal sequence, a DNAmolecule encoding a catalytic domain of a fungal exo-cellobiohydrolase,a DNA molecule encoding a catalytic domain of an endoglucanase, and aterminator.
 16. The vector according to claim 15 further comprising aselectable marker.
 17. The vector according to claim 15 furthercomprising a linker located 3′ of the exo-cellobiohydrolase (CBH)catalytic domain and 5′ of the EG catalytic domain.
 18. The vectoraccording to claim 15 further comprising a kexin site.
 19. The vectoraccording to claim 15 wherein the catalytic domain of the endoglucanaseis derived from a bacterial endoglucanase.
 20. A fungal host celltransformed with a heterologous exo-endo cellulase fusion constructaccording to claim
 1. 21. A fungal host cell transformed with a vectoraccording to claim
 15. 22. A recombinant fungal cell comprising theheterologous exo-endo cellulase fusion construct according to claim 1.23. A recombinant fungal cell comprising a vector according to claim 15.24. The recombinant fungal cell according to claim 22 wherein the fungalhost cell is a Trichoderma host cell.
 25. The recombinant fungal cellaccording to claim 22 wherein the fungal host cell is a strain of T.reesei.
 26. The recombinant fungal cell according to claim 22 wherein atleast one gene selected from the group consisting of the cbh1, cbh2,egl1 and eg/2 has been deleted from the fungal cells.
 27. An isolatedcellulase fusion protein having cellulolytic activity which comprises anexo-cellobiohydrolase catalytic domain and an endoglucanase catalyticdomain.
 28. The isolated cellulase fusion protein according to claim 27wherein the exo-cellobiohydrolase is a CBH1.
 29. The isolated cellulasefusion protein according to claim 27 wherein the catalytic domain of theendoglucanase is derived from a bacterial cell.
 30. The isolatedcellulase fusion protein according to claim 29 wherein bacterial cell isa strain of Acidothermus cellulolyticus.
 31. A cellulolytic compositioncomprising the isolated cellulase fusion protein according to claim 29.32. A method of producing an enzyme having cellulolytic activitycomprising, a) stably transforming a filamentous fungal host cell with aheterologous exo-endo cellulase fusion construct according to claim 1;b) cultivating the transformed fungal host cell under conditionssuitable for said fungal host cell to produce an enzyme havingcellulolytic activity; and c) recovering said enzyme.
 33. The methodaccording to claim 32 wherein the filamentous fungal host cell is aTrichoderma cell.
 34. The method according to claim 32 wherein thefilamentous fungal host cell is a T. reesei host cell.
 35. The methodaccording to claim 32 wherein the exo-cellobiohydrolase is a CBH1 andthe endoglucanase is selected from the group consisting of anAcidothermus cellulolyticus endoglucanase and a Thermobifida fuscaendoglucanase.
 36. The method according to claim 32 wherein therecovered enzyme is selected from the group consisting of a cellulasefusion protein, components of the cellulase fusion protein, and acombination of the cellulase fusion protein and the components thereof.37. The method according to claim 32 wherein the recovered enzyme(s) ispurified.
 38. A Trichoderma host cell which expresses a cellulase fusionprotein, wherein said fusion protein comprises a catalytic domain of anexo-cellobiohydrolase and a catalytic domain of an endoglucanase. 39.The Trichoderma host cell according to claim 38 wherein the host cell isa T. reesei cell.
 40. The Trichoderma host cell according to claim 38wherein the exo-cellobiohydrolase is a CBH1 and the endoglucanase is anAcidothermus cellulolyticus endoglucanase.
 41. The Trichoderma host cellaccording to claim 38 wherein the endoglucanase is either anAcidothermus cellulolyticus E1 or GH74 endoglucanase.
 42. TheTrichoderma host cell according to claim 38 wherein at least one geneselected from the group consisting of the cbh1, cbh2, egl1 and egl2 hasbeen deleted from the host cell.
 43. A fungal cellulase compositioncomprising a cellulase fusion protein or components thereof, wherein thefusion protein or components thereof is the product of a recombinantTrichoderma spp. according to claim
 38. 44. A fungal cellulasecomposition according to claim 43 wherein the cellulase fusion proteinis a CBH1-Acidothermus cellulolyticus E1 fusion protein and thecomponents are the cleaved products, CBH1 and Acidothermus E1.